In teleoperated robotically assisted surgery, the surgeon typically operates a master controller to control the motion of surgical instruments at the surgical site from a location that may be remote from the patient (e.g., across the operating room, in a different room or a completely different building from the patient). The master controller usually includes one or more hand input devices, such as handheld wrist gimbals, joysticks, exoskeletal gloves, handpieces, or the like, which are operatively coupled to the surgical instruments through a controller with servo motors for articulating the instruments' position and orientation at the surgical site.
The servo motors are typically part of an electromechanical device or surgical manipulator arm (“the slave”) that includes a plurality of joints, linkages, etc., that are connected together to support and control the surgical instruments that have been introduced directly into an open surgical site or through trocar sleeves (cannulas) inserted through incisions into a body cavity, such as the patient's abdomen. There are available a variety of surgical instruments, such as tissue graspers, needle drivers, electrosurgical cautery probes, etc., to perform various functions for the surgeon, e.g., retracting tissue, holding or driving a needle, suturing, grasping a blood vessel, dissecting, cauterizing, coagulating tissue, etc. A surgeon may employ a large number of different surgical instruments/tools during a procedure.
This new surgical method through remote manipulation has created many new challenges. One challenge is providing the surgeon with the ability to accurately “feel” the tissue that is being manipulated by the surgical instrument via the robotic manipulator. The surgeon must rely on visual indications of the forces applied by the instruments or sutures.
Various attempts to measure the forces and torques and to provide feedback to a surgeon have been made. One device for this purpose from the laboratory of G. Hirzinger at DLR Institute of Robotics and Mechatronics is described in “Review of Fixtures for Low-Invasiveness Surgery” by F. Cepolina and R. C. Michelini, Int'l Journal of Medical Robotics and Computer Assisted Surgery, Vol. 1, Issue 1, page 58, the contents of which are incorporated by reference herein for all purposes. However, that design disadvantageously places a force sensor distal to (or outboard of) the wrist joints, thus requiring wires or optic fibers to be routed through the flexing wrist joint and also requiring the yaw and grip axes to be on separate pivot axes.
As described in A. Dalhlen et al., “Force Sensing Laparoscopic Grasper,” U. Wisconsin Coll. Eng., Apr. 28, 2006 (http://homepages.cae.wisc.edu/˜bme402/grasping_instrument_s06/reports/Final_Paper.pdf), a team at the Univ. of Wisconsin led by A. Dahlen and advised by W. Murphy considered strain gauges on several parts of the jaw actuation mechanism of a manual laparoscopic bowel grasper finally settling on the hand grip. Also, as described at Paragraph 4.2, Medical Robotics, I-Tech Education and Publishing, Vienna, Austria, Pg. 388, (2007) (ISBN 13: 978-3-902613-18-9), U. Seibold et al at the German DLR Institute similarly measured the gripper actuation cable tension to calculate the grip force.
F. van Meer at LAAS/CNRS (2004) in Toulouse France pursued and patented what is described as a MEMS 2D silicon force sensor cemented to the inner surfaces of opposing folded sheet metal jaws of a five millimeter (mm) instrument and connected by ten wires. The sensor is capacitive and requires capacitive readout electronics located nearby. See Van Meer, et al., “2D Silicon Macro-force Sensor For a Tele-operated Surgical Instrument,” Proc. 2004 Int'l Conf. on MEMS, Nano and Smart Systems, (2004) (ICMENS-04). U.S. Pat. No. 6,594,552 to Nowlin et al. (2003) describes a method of governing grip force without jaw sensors and instead is based on a position control loop of the instrument jaws with the robot master grip command force dependent on springs resisting closure of the master finger levers.
G. Fischer et al., at Johns Hopkins University, (2006) attached strain gauges and blood oxygen sensors with lead wires to the leaves of a fan retractor to measure surgical forces (not grip forces) and resulting ischemia in liver tissue. See Fischer et al, “Ischemia and Force Sensing Surgical Instruments for Augmenting Available Surgeio Information,” ERCCIS-JHU, Int'l Conf. on Biomedical Robotics and Biomechatronics (BioRob) (February 2006).
E. Dutson et al., at UCLA, (2005) applied wire connected pressure sensing pads to the inner faces of a daVinci robotic surgical instrument and displayed the resulting contact force signal to the surgeon using a pneumatically actuated pad on the robot master finger levers. See Dutson E P, Hwang R, Douraghy A, Zhang J, Vijayaraghavan A, Gracia C, Grundfest W, “Haptic feedback system for robotic surgery,” Society of American Gastrointestinal and Endoscopic Surgeons (SAGES) 2005 Annual Meeting, Ft. Lauderdale, Fla., (Apr. 13-16, 2005).
U.S. Pat. No. 7,300,450 to Petronella et al. (2007) describes a laparoscopic instrument with a jaw force sensor comprising an optic fiber passing into a moveable jaw and aimed a reflecting surface on the jaw so that the amount of light reflected varies with the force on the jaw.
Each of these methods has shortcomings. For example, gripper jaw actuator cable forces do not measure the effects of jaw pivot friction which rises as the jaw actuation force increases. Contact sensors applied to the instrument jaw working face are subject to high contact pressures that may damage the sensor. An optic fiber or wires passing through the instrument wrist to a jaw sensor is liable to breakage.